Indirect air cooling method and system for working medium adopting parallel-connection positive and reverse refrigeration cycle

Abstract

The invention discloses an indirect air cooling method and a system with the working fluid of parallel-connected obverse and inverse refrigeration cycles. Based on the phase transition in the working fluid cooling process, a double-phase transition heat exchanger and a single-phase transition heat exchanger are respectively coupled with an obverse refrigeration cycle and an inverse refrigeration cycle which are connected in parallel; the saturated gaseous refrigerant from the phase-transition heat exchangers is compressed, boosted and then sent to an air-cooled radiator for exothermic condensation, then the condensed refrigerant enters a liquid storage tank and is decompressed through a throttle valve and sent to the phase-transition heat exchangers so as to complete the obverse refrigeration cycle; or the saturated gaseous refrigerant from the phase-transition heat exchangers is throttled and decompressed through a thermal expansion valve and then sent to the air-cooled radiator and the liquid storage tank, pressurized by a booster pump and finally sent back to the phase-transition heat exchangers so as to complete the inverse refrigeration cycle. The method and the system can bewidely applied to the cooling systems of the condensers in thermal power, nuclear power and other turbine-generator units or the cooling systems of the intercoolers in petroleum, chemical and other industries to reduce energy consumption, save investments, as well as improve water-saving rate and the adaptability of the cooling system to the environment; therefore, the method and the system are provided with promotional values and can produce larger social environmental benefits and economic benefits after implementation.

Description

technical field [0001] The present invention relates to the condenser of thermal power, nuclear power, gas-steam combined cycle and integrated coal gasification power generation, or large and medium-sized coolers in various industries such as petroleum, chemical industry, metallurgy, textile, papermaking, food, pharmaceuticals, etc. The invention relates to an indirect air cooling method and system for a cooled process medium (referred to as working medium), specifically an indirect air cooling method and system for working medium using parallel forward and reverse refrigeration cycles. Background technique [0002] Exhaust steam condensers of thermal power, nuclear power, gas-steam combined cycle and integrated coal gasification power generation, as well as large and medium-sized coolers in petroleum, chemical, metallurgy, textile, paper, food, pharmaceutical and other industries The cooling and condensation system of the working medium in the thermal system can be divided ...

AI Technical Summary

Problems solved by technology

[0007] However, the following shortcomings specific to the direct dry cooling system make it unable to adapt to the common pursuit of the current global power industry - the demand for "consumption reduction" and "emission reduction":

[0008] ①The water saving rate is not high enough, there is still room for improvement of 16-34%; ②The coal consumption is high, and the steam turbine exhaust pressure (back pressure) of the direct dry cooling system is usually much higher than that of the wet cooling system. For example, according to Gu Deming and Peng Zeying in " According to statistics in the fourth issue of "Thermal Turbine" volume 35 "Problems and countermeasures faced by the development of air-cooled steam turbines", the exhaust pressure of the direct dry cooling system is generally 9-40KPa, which is 2-3 times that of the wet cooling system. The back pressure leads to a loss of about 5-8% of the effective enthalpy drop of the steam turbine, a decrease of about 3-5% in the thermal efficiency of the cycle, and an increase of about 3-8% in the coal consumption of power generation; ③The investment is large, and usually the current price of a direct dry cooling system is about the same capacity The wet-cooling system is more than double that of the wet-cooling system; ④ takes up a lot of space, and the direct dry-cooling system occupies the lowest area in the dry-cooling system, but taking the subcritical 600MW unit as an example, the direct dry-cooling system is still 12 times the space required by the wet-cooling condenser of the same capacity. Need to occupy 36,000 m 3 ⑤ Poor environmental adaptability, antifreeze is required at low temperature, and it is difficult to run at full capacity at high temperature (that is, it cannot operate at full load). Sensitivity to change is high

[0012] ① High water consumption. According to the data provided by the "Statistical Table of Air-cooled Unit Situation Survey Data" distributed by the Science and Technology Service Center of the China Electricity Council during the National Thermal Power Air-cooled Unit Technical Exchange Conference, the water-saving rate of the indirect dry-cooled system is generally only 66%. -69%; while the highest water saving rate of the direct dry cooling system in China can reach 84%, and the highest water saving rate in foreign countries is only 90%; ②The indirect dry cooling system occupies more land than the direct dry cooling system; ③Indirect dry cooling system investment is more direct The dry cooling system is large; ④The cooling tower of the indirect dry cooling system has water mist discharge, which wastes water and pollutes the environment

However, it cannot change the phenomenon that the exhaust temperature of the steam turbine increases with the increase of the ambient temperature. Therefore, compared with the existing direct cooling system, there are still defects such as high coal consumption, difficulty in high temperature, and antifreeze at low temperature.

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